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I live all of the way down here in New Orleans, Louisiana. I am so tired of being eaten alive by mosquitos. I am told that Tansy, Citronella Grass and Basil will help. Is this true?

There are many herbs that have been proposed as mosquito repellents. Few, however, have proved to be effective enough to be used for this purpose in the landscape. The citrosa geranium was for several years widely marketed for this purpose, but tests have not borne out the hype. Citrosa, like most of the purported mosquito repellents, needs to be brushed against in order to release the repellent oils in the leaves. Whether enough is released from citrosa to have much effect is unlikely.

In tests at the University of Guelph, citrosa geranium was compared with lemon thyme in mosquito trials. Lemon thyme proved to be more effective, though still not adequate to completely repel mosquitos. Lavender was also partially effective. Lemon thyme is more practical to grow because the low growing varieties are suitable as ground covers and along pathways where they are likely to be trodden on causing the oils to be released.

Neem has also been proposed as a mosquito repellent, but it is not hardy in your area.

Tansy is known as an ant repellent. We have not heard that it repels mosquitos also.

Citronella grass is the source of the citronella oil used in mosquito repellent candles. While the oil is effective in repelling mosquitos, it is unclear to us whether the plants, grown in the garden, would release enough oil to have an effect.

Basil has a reputation as a mosquito repellent. There are many varieties of basil and the ones most often suggested as having repellent properties are lemon basil, cinnamon basil and Peruvian basil (Ocimim micranthum) -- a variety we no longer carry. Again, the challenge is to get herbs to release their oils to the atmosphere where the mosquitoes are flying, and the basils are not as likely to do so as the ground cover herbs such as lemon thyme.

One plant that is worth trying is yarrow. The people of Lapland in Scandinavia have long used extracts of the leaves as a mosquito repellent. Yarrow can also be grown as a ground cover and lawn replacement, though we are not sure how well it grows in coastal Louisiana.

Also, what are your warranties on the plants you sell? I’d love to get some rosemary too.

We do not offer a blanket unconditional warranty on herb plants because there are many things that can lead to failure, including improper watering and care. But we do have a generous replacement policy and we try to make ordering from Richters a pleasant experience for our customers.

We have a good selection of rosemary varieties. Rosemary is the International Herb Association’s Herb of the Year for 2000. We are pleased to offer a good selection in anticipation of the next year’s festivities.